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    Grafting of perylene and naphthalene fluorophores onto chitosan for improved thermal, optical and electrical properties
    (Polymer Society of Korea, 2024) Temurlu, Selin; Abureesh, Mosab A. A.; Abourajab, Arwa; Karşılı, Pelin; Dinleyici, Meltem; Altınışık, Sinem; Koyuncu, Sermet
    The grafting of N-(4-hydroxyphenyl)-3,4,9,10-perylenetetracarboxylic-3,4-anhydride-9,10-imide (4) and N-(4-hydroxyphenyl)-1,4,5,8-naphthalenetetracarboxylic-1,8-anhydride-4,5-imide (8) onto low-molecular-weight chitosan (5) was performed. The fluorescence, stability, electroactivity, conductivity, and solubility properties of the grafted chitosan polymer 9 were highly enhanced compared to the original chitosan. The weight-average molecular weight (Mw) of 19,800 g/mol was obtained. Grafted chitosan has even more excellent thermal stability with a higher initial decomposition temperature of 285 degrees C and char yield at 900 degrees C up to 73%. The fluorescence quantum yield efficiencies for polymer 9 are very high in all studied solvents (70% in CH3CN). The polymer showed five stepwise, fast, reversible one-electron reductions in electrochemical investigations due to the conductive fluorophores 4 and 8. The HOMO/LUMO levels were calculated as - 5.56 and - 4.14 eV, corresponding to the low band gap of 1.42 eV. The spectroelectrochemistry investigations confirmed the nature of the electron transfers. The morphological characterization using AFM, SEM, and TEM methods indicated a highly crystalline character of the grafted chitosan. The modified chitosan has the potential to be applied in various organic photonics and as a significant substrate material.
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    Öğe
    Synthesis, photophysical, electrochemical and morphological properties of a novel cross-linked chitosan-based fluorescent polymer: A fluorescence sensor for single-stranded DNA
    (Pergamon-Elsevier Science Ltd, 2023) Yucekan, Ilke; Dinleyici, Meltem; Temurlu, Selin; Rashid, Rebwar; Bodapati, Jagadeesh B.; Al-Khateeb, Basma; Abourajab, Arwa
    This report details the first-time use of the perylene-3,4,9,10-tetracarboxylic dianhydride as a cross-linker to synthesize a novel fluorescent, chitosan-based cross-linked polymer (3). The polymer has single-stranded DNA (ssDNA) binding properties that can be used in sensor production for detecting salmon sperm DNA. Chitosan polymer's solubility is poor and restricted to only acidic media. In contrast, this new fluorescent chitosan polymer was soluble in various organic solvents and aqueous solutions at different pHs. Its absorption, photo physical, electrochemical and morphological properties were investigated in detail. Gel permeation chromatography determined the weight average molecular mass (Mw) of polymer 3 as 21300 g/mol. Seventeen hydrophobic perylene units were determined in the cross-linked network. The energy levels of the highest occupied molecular orbitals and lowest unoccupied molecular orbitals of the new polymer 3 were calculated as-6.24 and-3.96 eV, corresponding to the band gap of 2.28 eV. Fluorescence and ultraviolet spectroscopy techniques were used to study the interaction between ssDNA and polymer 3. The interaction pointed to the intercalative mode, and the cross-linked chitosan can be used as a stable and sensitive platform for ssDNA detection. These results show a new class of organic biopolymers that could yield promising potential in many biomedical applications.